Railroads are under increasing pressure to reduce emissions and to increase fuel efficiency. One of several responses to these forces has been the development of hybrid locomotives. Donnelly has disclosed the use of a battery-dominant hybrid locomotive in U.S. Pat. No. 6,308,639 which is incorporated herein by reference. Hybrid locomotives can reduce emissions and fuel consumption in rail operations such as yard switching but they are less effective for medium haul freight or commuter trains.
In U.S. patent application Ser. No. 11/200,881 filed Aug. 19, 2005 entitled “Locomotive Power Train Architecture”, Donnelly et al. have further disclosed a general electrical architecture for locomotives based on a plurality of power sources, fuel and drive train combinations. The power sources may be any combination of engines, fuel cells, energy storage and regenerative braking. This application is also incorporated herein by reference.
The development of multi-engine locomotives is another response to the search for more energy efficient and emissions compliant locomotives. In U.S. patent application Ser. No. 11/201,267 filed Aug. 9, 2005 entitled “Multiple Engine Locomotive Configuration”, Donnelly et al. have disclosed a means of packaging engine modules on a multi-engine locomotive that optimizes the power density of the locomotive power plants while reducing emissions and fuel consumption. In a U.S. patent application Ser. No. 11/412,071 filed Apr. 25, 2006 entitled “Multiple Prime Power Source Locomotive Control”, Donnelly et al. further disclose a general means for controlling and balancing a number of prime power sources powering a locomotive, including control for various operating modes such as for example, (1) a maximum fuel efficiency mode; (2) a minimum emissions mode (whether of a substance or energy, such as noise); (3) a combination mode of good fuel efficiency and low emissions; (4) a maximum power mode; and (5) an optimum engine lifetime mode.
There are a number of practical considerations that need to be considered in implementing control schemes for multi-power source locomotives. For example, if diesel engines are used, strategies must be developed to ensure the engines are not turned on and off too frequently. As another example, maximum tractive effort may be required in low speed yard switching work; maximum fuel economy may be required in short haul medium speed operations; maximum acceleration and maximum fuel economy may be required at different times in commuter operation; and various combinations of maximum fuel economy and minimum emissions may be required in different locations on long haul routes. These various operating modes cannot all be accommodated by a single notch power table prescription for selecting the number of engines, engine speeds and engine power levels. Thus there is a need for a practical method of selecting engine operating modes by the locomotive engineer that allows the performance benefits of a multi-engine locomotive to be realized.